1. Field of the Invention
This invention relates to a card including a rotatory system optical recording medium, particularly to a card having internally a rotatory system optical recording medium which can be used for cash card for bank, chart card for hospital, ROM card for electronic dictionary, etc.
2. Related Background Art
In the prior art, as an information recording medium, a card having a magnetic recording layer on one surface or a card having an optical recording medium adhered in the shape of a tape, etc. has been widely known. Writing and reading of the information in these cards are performed by moving linearly the card relative to the head for reading, but this method is limited in moving speed, and it is difficult to make higher the recording density due to inferior characteristics such as scanning precision, etc.. Further, increase of recording capacity is also limited.
On the other hand, an information recording medium in view of the above drawbacks has been proposed. As a card including a rotatory system optical recording medium in a case body, Japanese Laid-open Patent Publication No. 79581/1985 reports a card which performs recording and reproduction of information by rotating a rotatory system optical recording medium within a flat space, but in view of the state in which the card is carried, when the card is subjected to deformation such as bending, etc., rotation of the recordig medium may become impossible, or irregularity in rotation may occur, whereby stable recording and/or reproduction becomes impossible. Also, in the case of optical recording medium, since recording and/or reproduction are effected through a transparent window, there is involved the drawback that the sensitivity of the medium is susceptible to influence from damage, dust, fingerprints on the surface, etc.
Further, when the case body is desired to be formed to a thickness which is as thin as equal to cash card, magnetic card, etc., the rotatory system optical recording medium must be formed in as thin a plate as possible. Then, the optical path between the surface on the light transmission side and the recording layer becomes short, and therefore there is also involved the drawback that the medium is susceptible to the influence from the medium surface, flaw, dust, contamination, etc. during recording and/or reproduction of signals, whereby stable recording and/or reproduction cannot be performed.